1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and a fabricating method of an LCD capable of designing a fine pitch of a pad and an FCT (Film Carrier Tape) output line of a liquid crystal in applying an FCT such as a TCP (Tape Carrier Package), a COF (Chip On Film) or the like having 642 channels of a 35 mm size to a liquid crystal panel based on a liquid crystal display (LCD) of 17 inches or 19 inches, to thereby preventing the occurrence of a short phenomenon due to misalignment of the liquid crystal panel and the FCT.
2. Description of the Related Art
As the Information Age advances, demands for display devices are increasing in various forms, and various flat panel display devices such as LCDs, PDPs (Plasma Display Panels), ELDs (Electro Luminescent Displays), VFDs (Vacuum Fluorescent Displays), or the like, have been studied, some of which have been utilized as display devices in various equipments.
Of them, the LCD having the advantages that it has good picture quality, is light and thin, and consumes low power is commonly employed to replace CRTs (Cathode Ray Tubes) for a mobile video display device. Also, the LCD is used for a mobile device such as a monitor of notebook computers or for a monitor of TVs or computers for receiving and displaying broadcast signals.
In general, the LCD is formed such that two substrates each having electrodes thereon are attached in a facing manner, between which a liquid crystal material is injected, and voltage is applied to the electrodes to generate an electric field to move liquid crystal molecules to thereby display an image according to transmittance of light that varies.
The LCD includes a liquid crystal panel formed by injecting liquid crystal between two substrates, a backlight disposed under the liquid crystal panel and used as a light source, and a driver positioned at an outer edge of the liquid crystal panel and driving the liquid crystal panel.
Here, the driver includes a driving IC in which driving circuits are integrated to apply signals to gate and data wirings (or gate and data lines) of the liquid crystal panel, and the driving circuit is divided into a COG (Chip On Glass), a TCP, a COF, etc., according to how the driving ICs are mounted on the liquid crystal panel.
The COG includes a driving IC on an array substrate of the liquid crystal panel, so the volume of the LCD is increased. The TCP or the COF includes driving ICs by using a separate film, so the driving IC-installed film can be bent to a rear surface of the liquid crystal panel, making the LCD compact. Thus, recently the TCP or the COF is commonly used, and in general, the TCP or the COF is also called a film having the driving ICs installed therein.
The structure of the LCD using the COF will now be described with reference to the accompanying drawings.
FIG. 1 shows the structure of a general LCD, and FIG. 2 is a sectional view of taken along line I-I′ of a pad part and a COF attached to the pad part in FIG. 1.
With reference of FIGS. 1 and 2, the liquid crystal panel 10 includes an array substrate 11 and a color filter substrate 12 attached to each other with a uniform cell gap maintained therebetween, and a liquid crystal layer formed by injecting liquid crystal between the two substrate 11 and 12. In this case, the array substrate 11 has a larger area than the color filter substrate 12, so it has a non-image region that is not covered by the color filter substrate 12, on which a plurality of gate and data pads for applying signals to the liquid crystal panel are formed.
Here, the gate pads and data pads on the array substrate 11 are connected with output wirings formed at one side of the COF 30, and in this case the COF 30 includes input wirings formed to be separated from the output wirings, FCTs 31 formed as opened IC regions between the input wirings and output wirings, and driving ICs 32 mounted at the opened IC regions and driving a liquid crystal panel 10.
The input wirings formed at the other side of the COF 30 are connected with a PCB 20. A plurality of elements such as ICs (Integrated Circuits) are formed on the PCB 20 to form drivers, and the drivers generate various control signals and data signals for driving the liquid crystal panel 10 and transfer them to the liquid crystal panel 10.
An anisotropic conductive film (ACF) is commonly used to connect the COF 30 with the driving ICs 32 mounted thereon to the liquid crystal panel 10 and the PCB 20. The ACF, which is formed such that small conductive particles are included in a sort of thermosetting resin film, is attached on a pad of the liquid crystal panel 10 and that of the PCB 20. And then, the COF 30 is attached to fit the pads of the liquid crystal panel 10 and the PCB 20, and then thermo-compressed, so as to electrically contact with each other in a vertical direction.
In this case, however, when the pad of the liquid crystal panel 10 and the output wirings of the COF 30 are thermo-compressed during the TAB (Tape Automated Bonding) processing, a minute misalignment occurs due to heat expansion of the terminal as shown in FIG. 2.
If it is assumed that an overall size (L) of one COF 30 having 642 channels is 48 mm based on a 17-inch or 19-inch LCD like the related art LCD, pitches between the adjacent pads of the liquid crystal panel 10 and pitches between the adjacent output wirings are designed to be about 58 μm, so leeway can be secured to a degree in spite of such misalignment.
However, as efforts for reducing the fabrication cost of the LCD by cutting down the costs of the COF, in case of the 17-inch or 19-inch LCD, the overall size (L) of a single COF including the pad with 642 channels formed thereon and output wirings contacting with the pad of the liquid crystal panel is reduced from 48 mm to 35 mm, resulting in that pitches between the adjacent pads of the liquid crystal panel and pitches between the output wirings of the COF are accordingly reduced to 40 μm.
With the pitch of 40 μm uniformly maintained between the adjacent pads of the liquid crystal panel and between the adjacent output wirings of the COF, a short is generated between the mutually adjacent pads of the liquid crystal panel or between the output wirings of the COF, causing a defective LCD.